Pattern amplitude is related to pattern imitation during the song development of nightingales

Song intensity has been neglected in studies on the song development of osc ine birds. We analysed this ontogenetic trajectory in the singing of hand-r eared nightingales, Luscinia megarhynchos, from their earliest song vocaliz ations (subsong) through plastic singing, to their adult full song. Embedde d in an age-dependent increase in overall sound level, nightingales showed systematic amplitude differences within their song performances. Episodes o f song performance containing many imitations of acquired model songs (IPA phases) were produced with a higher amplitude than episodes with only few o r no imitations (UPA phases). Further analysis of song patterns revealed th at this difference was mainly due to the high number of imitations occurrin g during the IPA phases. However, unidentified patterns (UPA) that were voc alized during IPA phases had a significantly higher vocal amplitude than UP As vocalized during UPA phases. This finding indicates that, besides patter n-related amplitude differences, performance phases as a whole also differe d in amplitude. The consistent pattern- and phase-related differences in so und level indicate that the control of vocal amplitude should be viewed as an integrative part of the vocal learning process. (C) 2001 The Association for the Study of Animal Behaviour.